add cloudformation plugin

[fujiwara]

#207

cloudformation plugin introduces template functions cfn_output and cfn_export.

An example of CloudFormation stack template defines Outputs and Exports.

# StackName: ECS-ecspresso
Outputs:
  SubnetAz1:
    Value: !Ref PublicSubnetAz1
  SubnetAz2:
    Value: !Ref PublicSubnetAz2
  EcsSecurityGroupId:
    Value: !Ref EcsSecurityGroup
    Export:
      Name: !Sub ${AWS::StackName}-EcsSecurityGroupId

Load cloudformation plugin in a config file.

config.yaml

# ...
plugins:
  - name: cloudformation

cfn_output StackName OutputKey lookups OutputValue of OutputKey in the StackName.
cfn_export ExportName lookups exported value by name.

ecs-service-def.json

{
  "networkConfiguration": {
    "awsvpcConfiguration": {
      "subnets": [
        "{{ cfn_output `ECS-ecspresso` `SubnetAz1` }}",
        "{{ cfn_output `ECS-ecspresso` `SubnetAz2` }}"
      ],
      "securityGroups": [
        "{{ cfn_export `ECS-ecspresso-EcsSecurityGroupId` }}"
      ]
    }
  }
}